Earlier this week, the on-demand taxi service Uber brought on some big guns in Washington: the Franklin Square Group, a tech lobbying firm that also counts Apple, Google, Cisco, Intel and Cablevision among its clients. The subject: "innovation in the transportation marketplace," according to the filing, on which an Uber representative declined to elaborate.

D.C. in Uber's sights. But why? (Uber Facebook page) D.C. in Uber's sights. (Uber Facebook page)

Uber is no stranger to government scrapping, of course, having hired the best-connected political fixers it can find in all the cities where local regulators have thrown up roadblocks. So far, though, those fights have stayed strictly local. Taxicab policy lives on a municipal and state level -- the federal government isn't handing out medallions or requiring all cabs to be physically hailed.

So what could Uber possibly want in D.C.? So far, they've gotten nothing but love from the feds; the Federal Trade Commission came down on Uber's side in a local Washington spat, and CEO Travis Kalanick spends lots of time sitting on panels with journalists and politicians who seem simply honored by his presence. D.C. just doesn't seem like that big a threat. What's more, Kalanick professes to dislike the Washington game of getting the rules to favor one player or another, preferring to compete on the same terms as everyone else.

For some clues, we might actually look to Uber's habitual opponent: the taxi industry. On the federal level, the two sides may actually have similar interests in terms of getting rid of regulations on all kinds of livery cars. Accordingly, the Taxicab, Limousine and Paratransit Association has long had a presence in Washington, lobbying against gas taxes, renewable fuel standards, safety regulations and rules that would help cab drivers unionize, spending about $100,000 a year.

That isn't exactly covered by the "innovation within the transportation marketplace" description, though. For that kind of thing, we might turn to the suite of issues that concern startups generally, like patent trolls, rules governing smartphone apps -- even immigration, given the number of people Uber's looking to hire. These are all issues where Uber, as a high-visibility startup, could be a good corporate citizen on behalf of a large community of smaller businesses that certainly can't afford to keep a lobby shop on retainer.

The more likely answer, though, is that Uber is playing along with the wishes of its new sugar daddy: Google, which put $258 million into the company back in August, along with private equity firm TPG. Uber might be a good partner in helping stave off legislation that might restrict self-driving cars, for example, since it could have a mutual interest. Uber, along with Google, would likely want to preserve strong privacy rights in unfinished updates to cybersecurity and electronic-communications legislation -- people are probably less likely to use an app if they know it helps the government track their movements. And now, with Uber going international, it may also want to lobby for changes to tax laws that would allow it to bring all that income back to the United States without giving up a third of it to the Treasury.

Of course, we may be overthinking this. When you've raised more than $300 million and have a massively scaling business model that doesn't gel nicely with regulatory regimes and incumbent industries, it's worth dropping a few grand just to have someone watch your back.